sPHENIX discussion of software

[Joe Osborn <jdosbo AT umich.edu>]

Hi Stefan,

This definitely makes sense, and is a nice "back of the envelope" calculation to justify the efficiencies seen in the presentation. I think that in my talk (maybe not on my slides) I mentioned that probing a higher value of x leading to larger pT would probably lead to the observed behavior, but I wanted to double check with others to make sure that this was a reasonable way to interpret it. I think your calculation shows that it does make sense. Thanks for digging into it a little more quantitatively than I did!

Joe Osborn

---------------------------------------

Joe Osborn

Ph.D Candidate

University of Michigan

jdosbo AT umich.edu

(859) 433-8738

On Tue, Feb 14, 2017 at 3:50 PM, Stefan Bathe <bathe AT bnl.gov> wrote:

Dear Joe,

In your presentation on the photon-jet acceptance and efficiency, you raised the question whether the acceptance*efficiency at high pT appears unreasonably large (slide 5).  I think this is pure kinematics:

If you assume in some simple-minded model the protons consisting of three partons with 1/3 the proton momentum each, and a 2->2 process, then the scattered partons (the photon and the jet) each have momentum 33 GeV/c.  Now requiring a photon transverse momentum > 25 GeV/c makes the polar angle > sin^{-1} (25/33) = 49 degrees.  Pseudorapidity of 49 degrees is 0.78.  So all that’s needed is 6 GeV of the jet energy (your efficiency requirement) in a cone of R=0.2 (0.2+0.8=1) for the jet to fall into the sPHENIX acceptance.

(This is also roughly consistent with the acceptance*efficiency at 10 GeV/c:  here we have sin^{-1} (10/33) = 18 degrees, so eta = 1.86.  0.78/1.86 = 0.42, close to the efficiency you observe. (The drop-off right at 10 is because it’s equal to the cut-off of _reconstructed_ pT.))

Does this make sense?  Or were you explicitly worried that fluctuations of the proton momentum fraction should lead to a lower efficiency?

Regards,

Stefan 

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Stefan Bathe

Professor of Physics
Baruch College, CUNY

Baruch:                                     BNL:
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On Feb 14, 2017, at 6:28 AM, pinkenburg <pinkenburg AT bnl.gov> wrote:

Hello everyone,

 This is a reminder for the regular sPHENIX simulation and software meeting, Tue Feb 14th, 1PM EST @ 2-219. You can find the agenda (with already 1 talk) under:

https://indico.bnl.gov/conferenceDisplay.py?confId=2680

for which the common modification password is "1008"
•            For residents at BNL, we will meet at the 2-219 conference room
•            To join the Meeting via phone bridge:  https://bluejeans.com/619960505 
•            To join via Phone:

1) Dial:

        +1.408.740.7256
        +1.888.240.2560(US Toll Free)
        +1.408.317.9253(Alternate number)
       (see all numbers - http://bluejeans.com/numbers)

2) Enter Conference ID: 619960505

See you/talk to you later

Chris

-- 
*************************************************************

Christopher H. Pinkenburg	;    pinkenburg AT bnl.gov
				;    http://www.phenix.bnl.gov/~pinkenbu

Brookhaven National Laboratory	;    phone: (631) 344-5692
Physics Department Bldg 510 C	;    fax:   (631) 344-3253
Upton, NY 11973-5000

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